Photoelectrochemical Detection of Calcium Ions Based on Hematite Nanorod Sensors.

α-FeO (hematite) thin films have been shown to be a robust sensor substrate for photoelectrochemical imaging with good stability and high spatial resolution. Herein, one-dimensional (1D) hematite nanorods (NRs) synthesized via a simple hydrothermal method are proposed as a substrate which provides nanostructured surfaces with enhanced photocurrent responses compared to previously described hematite films, good stability, and excellent spatial resolution for potential imaging applications. The photoelectrochemical sensing capability of hematite NRs was demonstrated by a high pH sensitivity without modification.

Photoelectrochemical imaging system with high spatiotemporal resolution for visualizing dynamic cellular responses.

Photoelectrochemical imaging has great potential in the label-free investigation of cellular processes. Herein, we report a new fast photoelectrochemical imaging system (PEIS) for DC photocurrent imaging of live cells, which combines high speed with excellent lateral resolution and high photocurrent stability, which are all crucial for studying dynamic cellular processes. An analog micromirror was adopted to raster the sensor substrate, enabling high-speed imaging.

Decellularized porcine xenograft for anterior cruciate ligament reconstruction: A histological study in sheep comparing cross-pin and cortical suspensory femoral fixation.

Aims: To evaluate graft healing of decellularized porcine superflexor tendon (pSFT) xenograft in an ovine anterior cruciate ligament (ACL) reconstruction model using two femoral fixation devices. Also, to determine if pSFT allows functional recovery of gait as compared with the preoperative measurements.

Methods: A total of 12 sheep underwent unilateral single-bundle ACL reconstruction using pSFT.

Use of a fluorescent probe to monitor the enhanced affinity of rh-BMP-2 to silicated-calcium phosphate synthetic bone graft substitutes under competitive conditions.

A comparative investigation was undertaken on 1-2mm sized granules of two forms of synthetic bone graft substitute (SBG) with identical pore structure but varied bulk chemistry, stoichiometric hydroxyapatite (HA) and silicate substituted (0.8wt% Si) hydroxyapatite (SA), to assess the influence of SBG chemistry on the relative affinity of an osteogenic growth factor (GF), recombinant human bone morphogenetic protein-2 (rhBMP-2). A previously described novel fluorescent probe, fluoresceinthioureidoaminocaproic acid (FTCA), was covalently attached to rhBMP-2 to give FTCA-rhBMP-2 and facilitate the quantitative monitoring of GF uptake and release from the two chemistries of SBG.

The effect of increased microporosity on bone formation within silicate-substituted scaffolds in an ovine posterolateral spinal fusion model.

This study compared the bone forming capacity of the same formulation of silicate-substituted bone graft substitute materials with different microporosity in an instrumented posterolateral spinal fusion ovine model. Materials with a strut porosity of (i) 22.5% (SiCaP) or (ii) 36.

Strontium substituted bioactive glasses for tissue engineered scaffolds: the importance of octacalcium phosphate.

Porous bioactive glasses are attractive for use as bone scaffolds. There is increasing interest in strontium containing bone grafts, since strontium ions are known to up-regulate osteoblasts and down regulate osteoclasts. This paper investigates the influence of partial to full substitution of strontium for calcium on the dissolution and phase formation of a multicomponent high phosphate content bioactive glass.

Efficacy of silicate-substituted calcium phosphate with enhanced strut porosity as a standalone bone graft substitute and autograft extender in an ovine distal femoral critical defect model.

A synthetic bone graft substitute consisting of silicate-substituted calcium phosphate with increased strut porosity (SiCaP EP) was evaluated in an ovine distal femoral critical sized metaphyseal defect as a standalone bone graft, as an autologous iliac crest bone graft (ICBG) extender (SiCaP EP/ICBG), and when mixed with bone marrow aspirate (SiCaP EP/BMA). Defects were evaluated after 4, 8, and 12 weeks with radiography, decalcified paraffin-embedded histopathology, non-decalcified resin-embedded histomorphometry, and mechanical indentation testing. All test groups exhibited excellent biocompatibility and osseous healing as evidenced by an initial mild inflammatory response followed by neovascularization, bone growth, and marrow infiltration throughout all SiCaP EP-treated defects.

Influence of cell culture medium composition on in vitro dissolution behavior of a fluoride-containing bioactive glass.

Bioactive glasses are used clinically for bone regeneration, and their bioactivity and cell compatibility are often characterized in vitro, using physiologically relevant test solutions. The aim of this study was to show the influence of varying medium characteristics (pH, composition, presence of proteins) on glass dissolution and apatite formation. The dissolution behavior of a fluoride-containing bioactive glass (BG) was investigated over a period of one week in Eagle's Minimal Essential Medium with Earle's Salts (MEM), supplemented with either, (a) acetate buffer, (b) 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer, (c) HEPES + carbonate, or (d) HEPES + carbonate + fetal bovine serum.

Development of novel fluorescent probes for the analysis of protein interactions under physiological conditions with medical devices.

In this article, a method to analyze protein adsorption on porous, clinically relevant samples under physiologically relevant conditions is described. The use of fluorescent probes was identified as a methodology that would facilitate analysis under a range of conditions including fully competitive conditions where a protein of interest may be labeled in isolation and then allowed to compete with unlabeled proteins on samples that require no specialized surface pretreatment. As a first step, this article describes the covalent labeling of isolated bovine serum albumin (BSA) with fluorescent fluoresceinthioureidoaminocaproic acid, FTCA, giving FTCA-BSA.

Microstructure and chemistry affects apatite nucleation on calcium phosphate bone graft substitutes.

The bioactivity of calcium phosphate bone grafts of varying chemistry and strut-porosity was compared by determining the rate of formation of hydroxycarbonate apatite crystals on the material surface after being soaked in simulated body fluid for up to 30 days. Three groups of silicate-substituted hydroxyapatite material were tested, with each group comprising a different quantity of strut-porosity (23, 32, and 46 % volume). A commercially available porous β-tricalcium phosphate bone graft substitute was tested for comparison.

Effect of increased strut porosity of calcium phosphate bone graft substitute biomaterials on osteoinduction.

The effect of increasing strut porosity on the osteoinductivity of porous calcium phosphate (CaP) and silicate-substituted calcium phosphate (SiCaP) bone substitute materials was investigated in an ovine ectopic model. One to two millimeter-sized granules or block implants with strut porosities of 10, 20, or 30% were inserted into the left and right paraspinalis muscle. At 12 weeks, histological sections were prepared through the center of each implant and bone contact, bone area and implant area quantified.

The osteoinductivity of silicate-substituted calcium phosphate.

Background: The osteoinductivity of silicate-substituted calcium phosphate and stoichiometric calcium phosphate was investigated with use of ectopic implantation. Implants with a macroporosity of 80% and a strut porosity of 30% were inserted into sites located in the left and right paraspinal muscles of six female sheep.

Methods: After twelve weeks in vivo, a longitudinal thin section was prepared through the center of each implant.

Development of a hydroxyapatite coating containing silver for the prevention of peri-prosthetic infection.

We hypothesized that the electrochemical deposition of hydroxyapatite (EHA) can be used to incorporate silver (Ag), providing a controlled and sustained release of Ag ions at a bactericidal concentration. Six groups were investigated: electrochemical co-precipitation of HA and Ag (EHA/Ag); EHA pre-coated discs treated in AgN0(3) (EHA/AgN0(3)); plasma sprayed HA (PHA) pre-coated discs treated in AgN0(3) (PHA/AgN0(3)); EHA with 2 "layers" of Ag (EHA/Ag/2 layers); EHA coating only; and PHA coating only. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses quantified coating thickness, calcium/phosphorous ratio, and % atomic silver content, respectively.

Effects of serum protein on ionic exchange between culture medium and microporous hydroxyapatite and silicate-substituted hydroxyapatite.

It has been proposed that one of the underlying mechanisms contributing to the bioactivity of osteoinductive or osteoconductive calcium phosphates involves the rapid dissolution and net release of calcium and phosphate ions from the matrix as alternatively a precursor to subsequent re-precipitation of a bone-like apatite at the surface and/or to facilitate ion exchange in biochemical processes. In order to confirm and evaluate ion release from sintered hydroxyapatite (HA) and to examine the effect of silicate substitution into the HA lattice on ion exchange under physiological conditions we monitored Ca(2+), PO(4)(3-) and SiO(4)(4-) levels in Earl's minimum essential medium (E-MEM) in the absence (serum-free medium, SFM) or presence (complete medium, C-MEM) of foetal calf serum (FCM), with both microporous HA or 2.6 wt% silicate-substituted HA (SA) sintered discs under both static and semi-dynamic (SD) conditions for up to 28 days.

Comparative performance of three ceramic bone graft substitutes.

Background Context: A number of different synthetic calcium-based bone graft substitutes (BGS) are currently available for clinical use. There is, however, a lack of comparative performance data regarding the relative efficacy of these materials when placed in an osseous defect site.

Purpose: To compare the rate, quality, and extent of osseous healing in a standard rabbit defect model for three commercially available BGS materials by measuring early bone formation and completion of defect healing and to identify whether rapid scaffold resorption stimulated or impaired bone healing.

Effect of silicon level on rate, quality and progression of bone healing within silicate-substituted porous hydroxyapatite scaffolds.

The osseous response to silicon (Si) level (0, 0.2, 0.4, 0.

Bone repair in the twenty-first century: biology, chemistry or engineering?

Increases in reconstructive orthopaedic surgery, such as total hip replacement and spinal fusion, resulting from advances in surgical practice and the ageing population, have lead to a demand for bone graft that far exceeds supply. Consequently, a number of synthetic bone-graft substitutes (BGSs) have been developed with mixed success and surgical acceptance. Skeletal tissue regeneration requires the interaction of three basic elements: cells, growth factors (GFs) and a permissive scaffold.

Mediation of bone ingrowth in porous hydroxyapatite bone graft substitutes.

Previous investigations have shown that both the early biological response and the mechanical properties of a porous hydroxyapatite bone graft substitute are highly sensitive to its pore structure. The objective of this study was to evaluate whether the pore structure continued to influence bone integration in the medium to long term. Two screened batches of porous hydroxyapatite (PHA) designated as batch A and batch B, with porosities of approximately 60 and 80%, respectively, were selected for this study and implanted for periods of 5, 13, and 26 weeks into the lower femur of New Zealand White rabbits.